The present invention relates to a thermoplastic and elastomeric composition and more particularly to a thermoplastic and elastomeric composition having high fracture resistances and suitable for use in the preparation of flexible parts such as a hose having excellent heat resistance, ozone resistance, oil resistance, etc.
In recent years, with respect to a rubber hose for automobiles, such as a fuel hose in contact with gasoline, studies have been made on the use of a polyamide resin hose for the purpose of improving the durability and reducing the weight and the cost. However, as opposed to the rubber hose, the polyamide hose is poor in the flexibility and large in the tension set, and in addition the polyamide resin is very poor in the resistance to the propagation of cracking and causes brittle fracture rather than ductile fracture, which makes it difficult to widely use the polyamide hose.
Attempts have been made at eliminating the above-described problem through addition of a plasticizer to the polyamide resin, conversion of the polyamide into a block copolymer comprising a polyether as a soft segment, and modification of the polyamide resin by blending of rubber with the polyamide resin. However, the addition of a plasticizer for eliminating the above-described problem causes the flexibility to be spoiled due to vaporization of the plasticizer through the action of heat and extraction of the plasticizer with an oil, which brings about a problem with respect to practical use. The conversion into a block copolymer brings about a lowering in the softening point, which renders the copolymer unsuitable for applications under high temperature conditions.
With respect to the modification of the polyamide resin by blending of the polyamide resin with rubber, proposals have been made on the blending by taking into consideration applications such as a fuel hose in contact with gasoline, and examples of these proposals include dynamic vulcanization blending of nitrile rubber (see U.S. Pat. No. 4,173,556), dynamic vulcanization blending of hydrin rubber (see U.S. Pat. No. 4,297,453), dynamic vulcanization blending of acrylic copolymer rubber (see U.S. Pat. No. 4,310,638), and dynamic vulcanization blending of nitrile rubber and hydrin rubber (see U.S. Pat. Nos. 4,661,563, 4,567,238, and 4,567,235). However, all of these methods have a drawback that the above-described blends are poor in the resistance to sour gasoline (gasoline containing a peroxide formed by the oxidation of gasoline), alcohol-mixed gasoline (gasohol), and sour alcohol-mixed gasoline (sour gasohol) which raised a problem in recent years.